Analysis of Heat Transfer Enhancement Mechanism on Flow Boiling in Vertical Rectangular Interconnected Microchannels
To enhance the wide application of flow boiling technology in the field of fuel cell heat dissipation,this paper uses R141b as the working medium to conduct three-dimensional transient numerical simulation of flow boiling in parallel straight channels and interconnected small channels at different flow rates.Parameters such as heat transfer coefficient,base temperature and comprehensive heat transfer factor are used to compare the heat transfer performance of each structure,and the heat transfer strengthening mechanism of interconnect small channels is explored.The results show that the heat transfer trend changes periodically with the bubble behavior,and the heat transfer effect is the best when the bubble is separated.The secondary flow caused by the connecting port promotes the heat transfer and wall temperature rise,so that the channel can meet the nucleation conditions 2 ms in advance,and the bubble breaks away first under the action of secondary flow rate above 1×10-4 m/s.Compared with the parallel straight channel,the heat transfer coefficient of five-connected channel can be increased by 19.6%～23.3%,and the relative growth rate of heat transfer coefficient is less than 3.5%as the number of connected channels continues to increase.The vortex structure leads to an increase in pressure drop with the increase of the number of connected channels,and the increasing trend does not diminish.The pressure drop of eight-connected channels is increased by 29.5%～42%compared with that of parallel straight channels.It can be seen that secondary flow not only affects bubble behavior and strengthens heat transfer,but also brings pressure loss.Comprehensive heat transfer performance is not positively correlated with the number of connecting vents.
国家科技期刊平台
NSTL
万方数据
